Controlling off-bottom position of pellet impact drill



Dec. 27, 1955 E. M. M NATT 5 CONTROLLING OFF-BOTTOM POSITION OF PEILLETIMPACT DRILL Filed July 15, 1953 2 Sheets-Sheet l EUGENE M. M NATTINVENTOR BY ATTORNEY Dec. 27, '1955 E. M. MONATT CONTROLLING OFF-BOTTOMPOSITION OF PELLET IMPACT DRILL 2 Sheets-Sheet 2 Filed July 15, 1953ATTORNEY 268,873 of Philip S. Williams, entitled CONTROLLING OFF-BOTTOMPOSITION PELLET IMPACT DRILL Eugene M. McNatt, Tulsa, Okla, assignor toEsso Research and Engineering Company, a corporation of DelawareApplication July 15, 1953, Serial No. 368,141

7 Claims. (Cl. 255-61) The present invention is concerned with a novelmethod and apparatus for the drilling of bore holes into the earthssubstrata. It is particularly concerned with an improved method andapparatus for the production of, or the recovery of oil from the earthssubstrata. The drilling method of the present invention employs novelprinciples to secure the recirculation and replenishment of solidpellets utilized in a bore hole for efiectively drilling the hole. Theforce of the pellets impinging on the bottom of the hole pulverizes theformation and materially aids in the drilling of the hole. Circulationof the pellets is maintained by a bit arrangement involving thepropulsion and recirculation of pellets in a fluid stream. Theparticular function of the present invention is to provide a novel andefiective means for controlling the oif-bottom position of the pelletimpact drill.

Basically the pellet impact technique for drilling bore holes in theearth involves the use of a stream of fluid pumped from the surface ofthe earth through a tubular member to a jet nozzle assembly adjacent thebottom of the bore hole. The jet nozzle assembly is adapted to direct ahigh velocity jet of fluid against the formation being drilled and isprovided with means for entraining in the jetted fluid a multitude ofpellets which are accelerated to high velocity in the jet stream andthereby acquire considerable kinetic energy so that when the pelletsimpinge against the formation the resulting percussive and fracturingforces exert a drilling action. Preferably the pellets that are employedare smooth, non-abrasive and essentially spherical and are ofsubstantial size, preferably in the size range of about A; inch to about1 inch or more in diameter. It is preferred that hard, dense, toughmetallic alloys be employed as the pellet material. The basic principlesof the technique of drilling by pellet impact are set forth inco-pending application, Ser. No. Pellet Impact Drilling Method andApparatus, filed January 29, 1952.

The effectiveness of pellet impact drilling is to a great extentdependent upon the distance the device is held off the bottom of thehole. If the drilling device is too close to the bottom or too far awayfrom the bottom, the efficiency of drilling drops off rapidly. It hasnow been discovered that the correct and most efficient positionoff-bottom for the device can be controlled by utilizing changes in thepressure differential across the wall of the secondary nozzle of thepellet impact bit.

The process and apparatus of the present invention may be fullyunderstood by reference to the various figures of the drawingillustrating embodiments of the same.

Figures 1-3 schematically represent the device attached to the lower endof a drill string in a bore hole at various positions with respect tothe bottom of the hole.

Figure 4 is a sectional elevation showing the details of one embodimentof the invention Figure is a section taken across line VV of Figure 4.

Figure 6 illustrates a modification of the device, this figureconstituting a sectional elevation of a structure States Patent 0 F2,72,557 Patented Dec. 27, 1955 substituted for the upper half of thestructure of Figure 4.

Referring specifically to Figures 1, 2 and 3, the principle of thevariation in the pressure dilferential across the walls of the secondarynozzle .f a gravity-aspirator type pellet impact bit is illustrated asthe bit is raised oil the hole bottom. With the bit resting on thebottom, as shown in Figure 3, the fluid pressure at A is greater than atB. On the other hand, because of the aspirator action of the jet as thebit is raised off bottom, as shown in Figure 1, the pressure at A willbe less than at B. It therefore follows that at some intermediateposition, as shown in Figure 2, the pressures must be equalized, atwhich point pressure A equals pressure B.

The use of this principle for securing the correct offbottom position isillustrated by Figure 4, showing one mechanism suitable for use. Thedevice shown in Figure 4 is depicted in its desired oif-bottom positionin a bore hole 50 being drilled by action of circulating pellets 55.Drill string 1 supports the entire assembly in the bore hole. Primarynozzle barrel 2 is slidably fitted on tubular support member 3. Cylinder4 is integrally attached to the support member at its upper end and atits lower end is slidably fitted to primary nozzle barrel 2. The upperend of primary nozzle barrel 2 terminates in piston 5, which fitsslidably within cylinder 4. Cylinder 4 has a channel 6 cut in it toprovide a fluid connection between the interior of support member 3 andannular chamber 8. Ports 7 provide a fluid passageway to equalize thepressure on the top side of piston 5 with that in bore hole annulus 9.The diameter of piston 5 is adjusted so that the upper thrust on piston5, when bleed port 30 is open is equal to the downward force on theprimary nozzle 10. This arrangement provides a neu trally stable,primary nozzle barrel 2 which will remain in a given position until thebalance of upward and downward thrusts is destroyed.

As illustrated by Figure 5, the secondary nozzle assembly comprises twopieces, 11 and 12, which are slidably fitted to each other. Element 12is rigidly fixed to nozzle barrel 2 by means of struts or web members 28The relative movements of parts 11 and 12 is limited to horizontaltranslation (as viewed in Figure 4-) by a plurality of pins 13, slidingin slots 14. Part 11 is fitted with slot 15 which slidably receives bellcrank 16. Pin 17 is attached rigidly to part 11 and passes through slot18 in the bell crank 16. Bell crank 16 pivots about pin 19 which isrigidly attached to web 21, which in turn is an integral part of nozzlebarrel 2. Pin 22 is a pivot pin connecting link 20 with bell crank 16. Ahousing 26 is provided which is attached to nozzle barrel 22 andsurrounds a portion of the lever mechanism comprising bell crank 16 andlink 20 to prevent damage by pellets or other solid material that may bepresent in the bore hole annulus. Spring 27 attached at one end to thenozzle barrel 2 and at its other end to lever 16 may be used in theevent that a preloading is desired on the bell crank lever 16. The upperend of link 20 is pivotally connected to slide valve 31 which serves toopen or close port 30. In operation, when the drill bit is too close tothe hole bottom, the pressure inside the secondary nozzle assembly 11-42increases. This causes outward motion of element 11 relative to element12, which in turn causes the linkage made up of lever 16 and link 20 tomove valve 31 upwardly and close port 36. This in turn causes thepressure in annular chamber 3 to increase, thus upsettingvthe balance ofupward and downward forces acting on nozzle barrel 2. This unbalancedupward force causes the nozzle barrel 2 to slide upwardly on supportmember 3 until the pressure inside secondary nozzle assembly 11-12decreases to the initial value. When this occurs, the desired off-bottomspacing will have been attained and the pressure diiferential across thesecondary nozzle wall will cause element 11 to move radially inward.This will open port 30. In the manner described, the bit will haveautomatically corrected for too short an off-bottom spacing.

To correct for too great an off-bottom spacing bell crank 16 has a slot23 cut in it through which pin 24 passes. Pin 24 in turn is attached tothe end of member 25. The other end of member 25 slidably fits in a slotin the primary nozzle 16. in operation, as the oft-bottom distanceincreases the pressure inside secondary nozzle assembly Iii-12 decreasesand the pressure differential across the nozzle wall causes element 11to slide toward element 12. Pin 17 causes bell crank 16 to move pin 24inwardly which moves the left end of member 25 into the primary jetstream. This increases the downward force on nozzle barrel 2 anddestroys the previous balance of force. Therefore, the nozzle barrel andentire bit will move downwardly until the desired cit-bottom position isattained. At this point the pressure differential across the wall of thesecondary nozzle will have moved element ll back to its originalposition, which will pull member 25 out of the primary jet stream andrestore the balance of up and down forces. Since these forces are inequilibrium the bit will come to rest at this position.

Referring specifically to Figure 6, illustrating an alternatearrangement which may be used to achieve the desired automaticcorrection for incorrect oil-bottom positions, this alternate device issimilar in many respects to that of Figure 4-. The major dilierencesbetween the structures are that valve 31 is replaced by the cylindricalslide valve E l that is capable of controlling port 39 in channel 6 aswell as controlling port 50, and that the spring 46 is placed underpiston 5. The device illustrated in Figure 6 will provide an upwardforce on nozzle barrel 2. which is independent of variations in fluidpressure. This is the function of spring 48. Spring 40 should be atleast ten times as long (in its unstressed position) as the length ofdeflection desired so as to require a relatively constant force for itsdeflection.

In the arrangement illustrated in Figure 6, the net area of piston 5 isconstructed so as to give a greater upward force than the downward forceexerted by fluid of equal pressure on primary nozzle 19. In operation,at the desired oil-bottom position, the total down load on nozzle barrel2 is balanced by a combination of upward forces due to spring ll and thefluid pressure in annular cham ber and the cylindrical slide valve 34 ispositioned so as to prevent fluid from entering or leaving annularchamber 8. Port 35 equalizes pressures on the top and bottom ofcylindrical slide valve 34. it" the oil-bottom spacing becomes toosmall, the pressure in secondary nozzle assembly ;i1l2 increases withthe resulting outward relative movement of member 3.1. This causes thebell crank it: (Figure 4) to move lint; 2t) upward. This in turn causesport 33 in slide valve 34 to come in line with port 39 which opens afluid passage into annular chamber 8. The result is that the fluidpressure in annular chamber 8 increases, forcing piston 5 upwardly. Whenthe bit has moved the necessary amount upwardly, the pressuredifierential across the wall of the secondary nozzle causes thecomponent 11 to return to its normal position which causes slide valve34 to close off port 39.

Therefore the upward motion of the bit stops and automatic adjustment ofoil-bottom position is secured.

if the bit is too far off bottom the pressure differential across thewall of the secondary nozzle causes component 11 to move inwardly. Thiscauses link 29 to be pulled downwardly, which in turn moves slide valve34 down until port 36 mates port 37 and provides a fluid passage out ofannular chamber 8. At the same time, member 25 (Figure 4) closes oil theprimary jet with the result that the downward forces overbalance theupward forces on nozzle barrel 2 and it moves downwardly until thedesired old-bottom position is attained. At this point, the

secondary nozzle member 11 will return to its normal relative positionrelative to member 12 (because of a change in the pressure differentialacross the nozzle wall) and hence the mechanical linkage willsimultaneously close port 37 and remove member 25 from the primary jet.Thus, the bit will come to rest at the new position which is the desiredoff-bottom position.

The device of the present invention also provides for sending anindication to the surface when nozzle barrel 2 has reached the lower andupper limits of its travel. When the lower limit of travel is reachedport 2% drops below the lower end of support member 3 and provides afluid passage from the interior of the support member to the annulus.This port 2) is of sufficiently large area to cause a noticeablepressure drop at the surface which indicates to the driller that theautomatic adjustment has reached the end of its travel and more pipemust be let down into the bore hole.

On the other hand, the upper limit of the travel of the bit is indicatedby a pressure rise. This is achieved as piston 5 approaches the upperlimit of its travel. Cam 32 on piston 5 engages cam 33 and causes cam 33to slide to the left and force plate 41 into the path of the fluid inthe drill string. The subsequent reduction of flow area in the drillstring causes the pressure to rise at the surface and thus warns thedriller, who can take the necessary action.

As pointed out before, the present invention comprises a method ofutilizing changes in the pressure differential across the wall of asecondary nozzle of a gravity-aspirator type bit in order to controlautomatically its oil-bottom position and thus insure efficientoperation at all times.

What is claimed is:

1. An apparatus for drilling a bore hole in the earth by pellet impactwhich comprises a tubular support member, a cylinder fixed to andsurrounding said support member, a nozzle barrel slidably surroundingsaid support member, said nozzle barrel terminating below said supportmember in a primary nozzle in fluid communication with the bore of saidsupport member and terminating at its upper end in a piston fittingslidably within said cylinder in a manner defining a first annularchamber below said piston between said cylinder and said nozzle barreland a second annular chamber above said piston between said cylinder andsaid support member, said cylinder having a lower exterior port intosaid first annular chamher, an upper exterior port into said secondannular chamber and a passageway establishing fluid communicationbetween said first annular chamber and the bore of said support member,a secondary nozzle fixed to said nozzle barrel and spaced below saidprimary nozzle, said secondary nozzle including a segment movable inresponse to changes in the pressure difierential across said secondarynozzle, and means controlling the opening of said lower port in responseto the motion of said movable segment.

2. Apparatus as defined by claim 1 including means controlling flowthrough said passageway in response to the motion of said movablesegment.

3. Apparatus as defined by claim 1 including means controlling fluidflow through said primary nozzle in response to the motion of saidmovable segment.

4. Apparatus as defined by claim 1 wherein said nozzle barrel isprovided with a port in the wall thereof so located that said port isclosed off by said tubular member except when said piston has moved to aposition adjacent its lowermost point of travel, whereby exposure ofsaid port will cause a drop in pressure within said support mem berindicative of said lowermost positioning of said piston.

5. Apparatus as defined by claim 1 including means for restricting flowthrough the bore of said tubular support member and means for activatingsaid flow restricting means when said piston has reached a positionadjacent its uppermost point of travel, whereby said flow restrictionwill cause a pressure buildup within the bore of said tubular supportindicative of said uppermost positioning of said piston.

6. Apparatus as defined by claim 1 wherein said means for controllingthe opening of said lower port comprises a slide valve and a leverlinking said slide valve to said movable nozzle segment in a mannercausing said slide valve to close said port on outward movement of saidsegment.

7. Apparatus as defined by claim 1 wherein said means for controllingthe opening of said lower port comprises a slide valve movable to afirst position closing said lower port and also said passageway, to asecond position opening said lower port while maintaining saidpassageway closed, and to a third position opening said passageway whilemaintaining said lower port closed, and a lever linking said slide valveto said movable nozzle segment in a manner moving said slide valvetoward said second position on outward movement of said segment, movingsaid slide valve toward said third position on inward movement of saidsegment and placing said valve in said first position when said segmentis intermediate its inwardmost and outwardmost positions of travel.

References Cited in the file of this patent UNITED STATES PATENTS1,659,826 Malloy et a1. Feb. 21, 1928

1. AN APPARATUS FOR DRILLING A BORE HOLE IN THE EARTH BY PELLET IMPACT WHICH COMPRISES A TUBULAR SUPPORT MEMBER, A CYLINDER FIXED TO AND SURROUNDING SAID SUPPORT MEMBER, A NOZZLE BARREL SLIDABLY SURROUNDING SAID SUPPORT MEMBER, SAID NOZZLE BARREL TERMINATING BELOW SAID SUPPORT MEMBER IN A PRIMARY NOZZLE IN FLUID COMMUNICATION WITH THE BORE OF SAID SUPPORT MEMBER AND TERMINATING AT ITS UPER END IN A PISTON FITTING SLIDABLY WITHIN SAID CYLINDER IN A MANNER DEFINING A FIRST ANNULAR CHAMBER BELOW SAID PISTON BETWEEN SAID CYLINDER AND SAID NOZZLE BARREL AND A SECOND ANNULAR CHAMBER ABOVE SAID PISTON BETWEEN SAID CYLINDER AND SAID SUPPORT MEMBER, SAID CYLINDER HAVING A LOWER EXTERIOR PORT INTO SAID FIRST ANNULAR CHAMBER, AN UPPER EXTERIOR PORT INTO SAID SECOND ANNULAR CHAMBER AND A PASSAGEWAY ESTABLISHING FLUID COMMUNICATION BETWEEN SAID FIRST ANNULAR CHAMBER AND THE BORE OF SAID SUPPORT MEMBER, A SECONDARY NOZZLE FIXED TO SAID NOZZLE BARREL AND SPACED BELOW SAID PRIMARY NOZZLE, SAID SECONDARY NOZZLE INCLUDING A SEGMENT MOVABLE IN RESPONSE TO CHANGES IN THE PRESSURE DIFFERENTIAL ACROSS SAID SECONDARY NOZZLE, AND MEANS CONTROLLING THE OPENING OF SAID LOWER PORT IN RESPONSE TO THE MOTION OF SAID MOVABLE SEGMENT. 